1. Field of the Invention
The present invention relates to a vehicle driving support apparatus for a vehicle having a cruise control function for constant speed cruise at a set vehicle speed set by a driver.
2. Description of Related Art
In recent years, there have been various proposals for driving support apparatuses configured to recognize a vehicle exterior environment in front of a subject vehicle by using a millimeter wave radar, an infrared laser radar, a stereo camera, a monocular camera or the like, and perform cruise control or the like of the subject vehicle based on the recognized vehicle exterior environment. As an example of such cruise control functions, a function of performing a follow-up cruise control to follow a preceding vehicle when such a preceding vehicle detected (captured) in front of a subject vehicle is known widely. Typically, the follow-up cruise control has been widely in practical use as part of an adaptive cruise control (ACC). In the ACC, the follow-up cruise control is performed in a state where a vehicle is detected in front of the subject vehicle, and a constant speed cruise control at a set vehicle speed set by the driver is performed in a state where no preceding vehicle is detected.
When the ACC is performed, speed limits for roads need to be observed. However, the speed limits vary depending on road types such as an expressway and an ordinary road, and may also be changed according to the weather or the like. Accordingly, the driver is always required to pay attention to the speed limit displayed on the road, and perform a troublesome operation to re-enter the set vehicle speed each time the speed limit changes. As a technique for reducing such a workload of the driver, Japanese Patent Application Laid-Open (JP-A) No. 2005-128790, for example, discloses a technique of recognizing a speed limit displayed on a road sign or a road mark based on an image in front of a vehicle captured by a CCD camera, accordingly updating with the obtained speed limit, and outputting an alarm when the vehicle speed exceeds the speed limit.
However, if the technique disclosed in JP-A No. 2005-128790 is applied to the ACC without any modification, the vehicle may be accelerated or decelerated against the intention of the driver when the set vehicle speed deviates largely from the speed limit.